Loop antenna



1942. L. H. VAN BILLIARD 2,292,182

LOOP ANTENNA Filed July 23, 1940 Inventor:

Lewis H. Van Bil liar-d,

Wifi w b5 His Attorney.

1942- L. H. VAN BILLIARD 2,292,182

LOOP ANTENNA Filed July 23, 1940 2 Sheets-Sheet 2 Inventor: Lewis H. Van Bil Hard,

l-lis A tor-neg.

Patented Aug. 4, 1942 LOOP ANTENNA Lewis H. Van Billiard, Newtown, Conn., assignor to General Electric Company, a corporation of New York Application July 23, 1940, Serial No. 346,905

2 Claims.

the same time possesses improved operating characteristics.

A further object of my invention is to provide an improved method of manufacture of such loop antennae.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 represents a radio cabinet housing a shielded loop antenna constructed in accordance with my invention; Figs. 2 and 3 illustrate details of my invention and Figs. 4, 5 and 6-illustrate the loop antenna in different stages of the method of manufacture in accordance with my invention.

Referring to Fig. 1 of the drawings I have illustrated therein a radio cabinet I having a radio receiver chassis 2 mounted on a shelf 3 therein. Beneath the chassis is a shielded loop antenna represented by the rectangle 4, this loop antenna being arranged for rotation about pivot members 5 and 6 by means of a suitable pulley and belt arrangement I controlled from the front of the cabinet.

It is now common practice to employ such loop antennae in radio receivers which may be oriented for minimization of undesired noise currents. An electrostatic shield generally of cylindrical form encloses the loop to reduce its socalled antenna effect thereby to render the null points of the loop more pronounced. Thus the loop may be oriented with its null points in the direction of propagation of waves representing undesired disturbances so that the loop has its minimum sensitivity to such disturbances. Since ordinarily the desired signal arrives at the loop from some other direction, it may have desired sensitivity to such desired signals.

Fig. 2 is a sectional view through the loop antenna 4 of Fig. 1. In this figure, two loops are shown, one being indicated at 8 and the other being indicated at 9. The loop 8 is mounted upon a flexible form which in turn is mounted upon a rigid form member I 0 which extends between two end walls I I and I2 of the housing for the loop.

The housing for the loop is comprised of these end Walls II and I2 plus a side wall, which may be cylindrical, comprising a shield I3. This shield may be of flexible material such as a suitable tough paper I 4 upon which is wound parallel conductors I5 which are covered by an additional coating as of paper I6, the two layers of paper being suitably cemented together to hold the wires in place. These conductors I5 extend around the circumference of the housing in parallel relation but are broken at one point in the circumference so as not to form an electrical circuit. They are then all connected together at one point and grounded to constitute an elec trical shield.

The end member I i has openings therein as indicated at I1 and I8 to receive ears I9 and 20 formed on the form member ID. Similarly, the end member I2 has openings 2| and 22 that re ceive ears 23 and 24 on the form member In whereby the form member is secured in place within the shield. The loop 8 may be connected between terminal members 25 and 25 for operation in the broadcast band. If desired, an intermediate point 21 thereof may be connected to a terminal member 28 extending to an external non-directive antenna whereby the loop may be used as a transformer for non-directional reception where minimization of noise is not of prime consideration. Such an arrangement is shown in Patent 2,222,709, George W. Fyler, granted November 26, 1940, and assigned to the same assignee as the present application. Loop 9 may similarly be connected between the terminal 25 and terminal 30 for operation in a short wave band, an intermediate point thereof being connected 'to a terminal 3| for non-directive reception.

Fig. 3 shows the structure in exploded fashion better to illustrate its assembly. The end walls II and I2 are shown removed from the shield I3 and the member Ii] carrying loops 8 and 9 is withdrawn from the shield. Also, the outer layer of paper I6 of the shield is shown torn away to expose the conductors I5 which are connected together by means of an additional conductor 32 Which may be grounded.

The loop 8 is shown mounted upon an endless strip of flexible material 33 the edge of which adjacent to form member I0 is bent inward at right angles to strip 33, as shown at 34, and these inwardly bent edges are stapled as at 35 to the form member III, or are otherwise suitably attached thereto as, for example, by gluing. In this way the flexible strip 33 which may itself be of paper is maintained in substantially rigid form so that the inductance of the loop remains satisfactorily constant during ordinary handling operations, etc., to which the receiver may be subjected.

The loop 9 is wound over ears 35 cut into the form member H], as is clearly shown in Figs. 2 and 3. The form It) has ears I9, 20, 23 and 24 which, when the loop is assembled, project through openings I1 and H3 in disk II and openings 2| and 22 in disk l2 whereby the form member I is held rigidly in place. The disks I l and I2 are provided with circumferential flanges 40 which are stapled to the upper and lower edges of the flexible shield member I3. Staples for this purpose are indicated at 4| in Fig. 2.

In Fig. 3 terminal 25 is shown connected to the terminal of the loop 8 remote from cardboard plate Hl. This terminal may be the high potential terminal of the loop which is connected to the grid or input electrode of the first discharge device of the receiver. The low potential terminal of the loop, or side adjacent cardboard I0, is connected to terminal 26 which may be connected to cathode of the first discharge device and grounded. The capacity of the loop is materially reduced and the efficiency of the loop substantially improved by this connection.

As thus assembled, the loop is of particularly economical construction. Its method of construction may best be illustrated by reference to Figs. 4, and 6. Fig. 4 illustrates at 42 a sheet of the flexible material on which the loop is wound wrapped about a mandrel 43 to form an endless layer. This mandrel may be a suitable mandrel in a coil winding machine. The outer surface of this flexible material 42 may then be gummed and a conductor 44 wound thereon in sections as indicated at 45, 46 and 41. After this has been done, a cutter of the coil winding machine indicated at 49 may be brought against the sheet of material to cut it into strips somewhat longer than the coil sections whereupon the different strips may be slipped off the mandrel in individual loop sections as indicated in Fig. 5. It will be noticed in Fig. 5 that the endless strip of the material 42 which may be paper, is somewhat wider than the width of the coil section 41. The loop being then of a flexible material may be formed in any desired shape as, for example, the rectangular shape shown in Fig. 6 and one edge of the strip may be bent inward as indicated at 34 to constitute a flange by which the loop may be attached to the form member II] in a manner shown in Figs. 2 and 3.

It has been found that loops constructed in this fashion are particularly advantageous in commercial production in that they may be manufactured with a minimum variation of inductance. In fact, it has been found that these variations may be made within tolerances narrower than is the case with loops of different construction. In addition, it has been found that when so assembled, the loops are of sufficient rigidity to resist deformation during service conditions with entire satisfaction. In addition, since all of the parts of the assembly may be made of paper and cardboard pressed and cut to shape, it will be readily appreciated that its construction is extremely economical. At the same time its rigidity is entirely adequate and satisfactory for all of the purposes of commercialization in broadcast receivers for home use.

While I have shown a particular form of my invention, it will, of course be understood that I do not wish to be limited thereto since different modifications may be made without departing from the spirit and scope of my invention, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A loop antenna structure for a radio receiver or the like comprising, in combination, a strip of flexible non-conducting material formed into a closed loop of a size sufficient to provide a supporting surface for the conductors of a loop antenna, said loop being narrow relative to its peripheral length, a conductor wound on the surface of said strip to form a loop antenna, said loop and said antenna possessing low resistance to deformation transversely of the surface of said strip, a rigid supporting member having a surface extending transversely of the axis of said strip at one edge thereof, said edge being bent at right angles to said strip and attached to said surface, thereby to give said flexible material and loop antenna substantial rigidity.

2. A loop antenna structure for a radio receiver or the like comprising, in combination, an endless strip of flexible non-conducting material formed into a cylinder of substantially rectangular cross-section, said strip being narrow relative to the lengths of its sides, a conductor wound on the surface of said strip to form a rectangular loop antenna, said loop and said antenna possessing low resistance to deformation transversely of the surface of said strip, a rigid form member lying in a plane transverse to the axis of said strip and adjacent one edge thereof, said strip being wider than said loop, and the portions of said strip extending beyond one edge of said loop and adjacent said supporting member being bent at right angles substantially along the entire periphery of said strip and attached to said form member, whereby said loop has substantial rigidity by reason of its attachment to said rigid form member.

LEWIS H. VAN BILLIARD. 

